The 6-cent stamp commemorating the 50th anniversary of the constitutional amendment that guaranteed American women the right to vote was first placed on sale on August 26, 1970, at Adams, Massachusetts. The 19th amendment was passed by Congress on June 4, 1919 and ratified on August 18, 1920. The amendment declared that "the right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex."
The stamp was designed by Ward Brackett and issued in panes of fifty, with an initial printing of 130 million.
Postal Bulletin (July 0, 1970).
National Archives and Records Administration. "Ourdocuments.gov." http://www.ourdocuments.gov/doc.php?flash=true&doc=63 (Accessed 24 April 2008)